[Review] IBM PS/2 P70/P75 keyboard (ALPS Plate Springs)

I'm well aware that this is an older review, originally posted 2011-03-07, but I'm migrating all of my reviews to Deskthority.

So, it's here. Time to review it. As I don't currently have a way of connecting it to a machine, I'm not going to review it in operation until that time. Pics will come later.

Build Quality
Man, this thing feels cheap. It's a lightweight plastic board, with very little metal reinforcement, and PCB mount switches. (The 5576-001 and 002, the other boards that use these switches, are plate mount, FWIW.) A lot of that is due to the need to save weight, however - it's designed to be part of a portable computer. It looks like it's been assembled quite well, however.

The Switches
If you're not familiar with plate spring switches, it's best to start out with the Qwerters Clinic article (Japanese-only, so here's a translation.)

Essentially, here's how it works:

Slider acts on coil spring
Coil spring acts on plate spring that is bowed upward
Plate spring, when pushed down, snaps downward into a plastic piece
Plastic piece pushes two contacts together

Releasing, the tension on the coil spring is reduced, causing the plate spring to snap upwards, freeing the plastic piece, breaking the contacts.

So, the plate spring is a beautifully lightweight (~60g, IIRC) switch with excellent tactile feel, slightly quieter (but higher pitched) than my EnduraPro, yada yada yada.

It has one Achilles' heel, though. (Not as bad as other switches, though.)

It actually starts to feel slightly mushy at speed (tactile events are still sharp when they happen, but the tactile event starts to move around). Wait, what? How can that be?

Simple. Note that the slider never directly acts upon the plate spring - it acts on it THROUGH a coil spring.

Therefore, there's two springs interacting when you're depressing the key.

I'll note that it isn't terrible - the Fujitsu Peerless has a similar problem, but it's far, far worse on the Peerless. Right now, I think I prefer the plate springs to Cherry blues. Think I like beam springs better, though, at this point. (I haven't extensively typed on the plate springs, though. Once I can get it interfaced to a computer, you bet I'll be typing on them a lot.)

Edit: On second thought, it is terrible. Not as terrible as the Peerless, true, but the tactile point moves based on how fast you're typing. That's unacceptable, I'm sorry.

Other impressions
This one, I left out of the switch impressions, because I think it's influenced by the keyboard's construction, but there is a bit of a "typing on cardboard" feel, that others have described out of a Model M2. I have no reason to believe that exists on the plate-mount boards using these switches, though.

The tilt mechanism is kinda clever, although it's huge.

Keycaps look decent quality - I'm guessing they're dye-sub, just like Model M keycaps.

Not sure I have much else to say until I get it working...
bhtooefr
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Unread post02 Apr 2012, 10:54

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bhtooefr
 
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Interesting, never noticed mushiness on this board. Maybe because I never really typed on them, just checking out keys. How did you connect it? Mine doesn't have a PS/2 connector on the cable, but the cable is PS/2? Review needs some pictures:

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webwit
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Unread post02 Apr 2012, 14:46

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I never connected it either, but Sandy's site has the pinout: http://sandy55.fc2web.com/keyboard/ibm_p7x_en.html

I find it hard to describe the behavior, because it isn't mushy, but at the same time it is.

I guess you could say... it's like you took Cherry blues, and instead of mounting them on a PCB, mounted the whole switch on top of a rubber dome? But less tactile than that? Whatever it was, I didn't like it. It's quite fatiguing to type on, due to way too high initial force.

I really do need to sell the thing - it's a freshly refurbed board that looks in great condition, and even if the switches suck it's useful for a specific highly collectible computer, so...
bhtooefr
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Unread post02 Apr 2012, 21:43

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I noticed it's slightly shorter travel.
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Unread post02 Apr 2012, 21:45

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I actually connected mine to my computer and used it for a while on Soarer's converter. Like any keyboard, one cannot accurately make a judgement until you use it. Using it for about four hours I still say my preferred order for IBM is:

Capacitive buckling spring
Membrane buckling spring
ALPS Plate Spring

Untried on a computer:
Beam spring

Ones I don't have:
ALPS BS "The Holy Grail" which I have a feeling if I find a SM-101 it will be my daily driver until I die. Right now I use a Unicomp "SpaceSaver" PS/2.
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Unread post03 Apr 2012, 16:47

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<~rms> while, acfrazier lives in PA
<~rms> where people are apparently insane
<~rms> and cats
You can accurately make a judgment when your fingers are stiffened up after a couple minutes of fast (even if it is nonsense) typing, when even an older M doesn't do that.
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Unread post03 Apr 2012, 16:53

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Best place for a Sega is Yahoo Auctions Japan. Had to look for it quite a while though.
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Unread post03 Apr 2012, 16:58

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There's one there right now in fact, but it's the full system.
002
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Unread post03 Apr 2012, 22:46

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And it's 50,000 yen. If I absolutely knew I loved the switch and didn't want anything else, I'd consider it, but that's too rich for my blood for a switch that I've never used before, and while I like the description a LOT, who knows, I might not like it in reality.
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Unread post04 Apr 2012, 01:45

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Might be purely theoretical, but honestly after reading the review again here I thought of something; when I type slowly I type [i]differently[i] then when I type at speed, so moving tactile points don't seem like an awful idea at all- or at least for as long as the activation point moves as well; or even if not, a keyboard that types differently at different speeds doesn't necesarily constitute a bad thing.
Would love to hear from someone who's seriously typed on this board (connected) for at least a week or three.. or any other alps plate or other *adaptive* switch.
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Unread post07 Apr 2012, 02:09

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